sustainability

Article

Monitoring and Assessment of Groundwater Quality at LandfillSites: Selected Case Studies of Poland and the Czech Republic

Anna Podlasek 1,* , Aleksandra Jakimiuk 1, Magdalena Daria Vaverková 1,2 and Eugeniusz Koda 1

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Citation: Podlasek, A.; Jakimiuk, A.;

Vaverková, M.D.; Koda, E.

Monitoring and Assessment of

Groundwater Quality at Landfill

Sites: Selected Case Studies of Poland

and the Czech Republic. Sustainability

2021, 13, 7769. https://doi.org/

10.3390/su13147769

Academic Editors: Marzena Smol,

Maria Włodarczyk-Makuła,

Joanna Duda and Ludwig Hermann

Received: 31 March 2021

Accepted: 9 July 2021

Published: 12 July 2021

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4.0/).

1 Department of Revitalization and Architecture, Institute of Civil Engineering, Warsaw University of LifeSciences, Nowoursynowska 159 St., 02-776 Warsaw, Poland; aleksandra_jakimiuk@sggw.edu.pl (A.J.);magdalena_vaverkova@sggw.edu.pl (M.D.V.); eugeniusz_koda@sggw.edu.pl (E.K.)

2 Department of Applied and Landscape Ecology, Faculty of AgriSciences, Mendel University in Brno,Zemedelská 1, 613 00 Brno, Czech Republic

* Correspondence: anna_podlasek@sggw.edu.pl

Abstract: In order to protect the components of natural environment, each landfill must be properlysecured and the monitoring program should be adopted. This study aims to present a comparativeanalysis of groundwater quality at selected landfill sites in Poland and the Czech Republic, with aspecial attention given to the levels and temporal changes of heavy metals (HMs) concentrationsmeasured in collected groundwater samples. A secondary objective was to detect possible leakagesof pollutants from the landfill body, into the groundwater, and further into the environment. Theassessment of groundwater quality was based on a comparison of HMs concentrations with standardsprovided by the European environmental laws. On the basis of the long-term monitoring period,it was revealed, for the Polish landfill site, that the groundwater quality is improving over time,especially due to remedial works applied. For the Czech landfill, it was observed that the qualityof groundwater is not negatively affected by the operation of the landfill, but in the immediatevicinity of the landfill, the groundwater quality is significantly affected by the agricultural use ofneighbouring lands, as well as by the storage of construction and demolition wastes. The resultsshowed that the leachate did not leak outside the landfills, especially due to minimal concentrationsof HMs, measured in groundwater samples, taken from the piezometers located in the outflowdirection from the landfills.

Keywords: contamination; groundwater; heavy metals; reclamation

1. Introduction

Landfilling in the 21st century is still the most common method of waste manage-ment [1,2]. Nevertheless, proper Circular Economy (CE) policies have contributed to arecent decreasing trend in European countries [3]. Landfills are sources of greenhousegases emissions [4] and possible threats to the aquatic environment, thus reduction andreclamation of landfill sites can be considered as a way to the implementation of Green Deal(GD) assumptions. The landfills have to be reclaimed in accordance with the GD strategies,including the application of environmentally-friendly technologies, and the solutions, then,can increase the protection of human health and the environment against hazardous andharmful substances arising from the landfill. The solutions (degassing systems, landfill gasdevelopment monitoring) should be applied to reduce methane emissions from the land-fills. Engineering activities should be also perform to restore ecosystems and biodiversityduring the biological reclamation of the landfills.

Urbanization and industrialization lead to the production of solid wastes that finallyare disposed to landfills [5–7]. Improper location and operation of landfills may negativelyaffect soil, flora, air, surface water, and groundwater [7,8]. The most significant problemrelated to municipal solid waste (MSW) landfills are leachates [9]. The leachates are com-posed of a complex of chemicals, including organic substances, inorganic and organic salts,

Sustainability 2021, 13, 7769. https://doi.org/10.3390/su13147769 https://www.mdpi.com/journal/sustainability

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and heavy metals (HMs), which vary in concentration depending on a set of factors [10].The composition of leachates is complemented by water, which constitutes 99% of theirvolume [11]. The leachates are formed as a result of rainwater seepage through the waste,biochemical processes occurring in the waste cells, and water in the waste itself [12]. Theleachates can carry insoluble liquids (e.g., oils) and suspended solids composed of smallparticles [13]. In case of inadequate landfill sealing, these substances could infiltrate intothe soil, contaminating groundwater for a long period of time [8]. The landfills, especiallythe old ones, without any protection systems applied, are most exposed to infiltration [14].

The landfills are also known as latent sources of HMs pollution in the environment.Due to a lack of drainage systems, landfills lead to the occurrence of toxic and threateningHMs in groundwater [15]. Therefore, landfill reclamation is a rescue for contaminatedgroundwater. Recently, it has been noted that the application of reclamation treatmentspositively affects groundwater quality [16]. The protection of water from contamination inadjacent areas can be applied by the construction of a vertical barrier, a component of whichis also a suitable leachate drainage system [17]. In addition to their sealing function and rolein preventing the migration of pollutants, the vertical barriers are also a tool for a CE. Thematerials of which the barriers are made are composed of mineral wastes and by-products,so they can be considered an excellent instrument of sustainable development (SD) [18]. Byadapting legislation, the CE strategy is simpler to implement. GD and CE strategies forlandfills are extremely important to reduce the negative interaction between the economy,the environment, and natural resources. The implementation of technologically innovativesolutions contributes to SD and continuous improvement of the environment. Meetingthe need for SD, it is desired to rehabilitate and close sanitary landfills. Moreover, wherepossible, it is also needed to use available resources from landfills.

Besides the introduction of additional technical seals in landfills, nowadays, thereare also more complex leachate transfer systems. In the past, in old Polish landfills, theleachate was mainly captured by drainage or by band ditches and stored in retention tanksand collection wells. Nowadays, the systems are more complex and also have recirculationelements, pumping stations for leachate transfer, pumping pipelines, and systems fordistribution of contaminated water on the surface of the landfill, with the possibility ofdilution for irrigation purposes [17].

Apart from leachate capture systems, groundwater monitoring is also extremely im-portant to ensure that leachate does not seep into the environment and cause harm tohuman health [13]. Groundwater monitoring should be performed at special measurementpoints, such as piezometers [11]. Each landfill should have at least three piezometers, withone located upstream and the others downstream from the landfill [11]. The Regulation ofthe Minister of the Environment on landfills [19] requires testing of groundwater parame-ters, such as pH, electrical conductivity (EC), total organic carbon (TOC), HM content, suchas copper (Cu), zinc (Zn), lead (Pb), cadmium (Cd), chromium (Cr+6), and mercury (Hg),and total polycyclic aromatic hydrocarbons (PAHs). Each country sets its limits that cannotbe exceeded. However, in the European Union (EU) they are very similar to each other.

This article presents a comparative analysis of groundwater quality at selected landfillsin two EU countries: Poland and the Czech Republic, which use different technical securingsystems [20,21]. The difference in applied securing systems is related to the technicalsolutions used in the base and cover systems. It was hypothesized that properly reclaimedand technically secured landfills do not pose the threat to the groundwater. Hence, the aimof the study was to assess the groundwater contamination by HMs at MSW landfills andsurrounding environment and to analyse the factors influencing contamination.

2. Materials and Methods2.1. Characteristics of the Study Sites2.1.1. Radiowo Landfill

The Radiowo landfill (52◦16′37′′ N, 20◦52′45′′ E) is located in the commune StareBabice and partially in Warsaw, Poland. The landfill covers an area of approximately 16 ha,

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and its altitude is approximately 60 m. The landfill is surrounded by Forest Park Bemowoand Nature Reserves from the south and east sides. From the north side, the landfill isadjacent to a composting plant located in the Warsaw–Bielany District. On the west side, inthe vicinity of the landfill slope, there are industrial facilities and a railway (Figure 1).

Figure 1. The view on the Radiowo landfill location together with its monitoring network and surroundings.

The landfill was constructed in the early 1960s when no legal restrictions, regardinglocation and environmental issues, were taken into consideration. The Radiowo landfillwas used for disposal of the municipal waste from Warsaw in the period 1962–1991.

The landfill area is located within a denuded glacial plateau defined as the Warsaw-Błonie erosion terrace. It is the central part of the Warsaw basin, characterized as syncline,in the Mesozoic formations. The syncline is filled with tertiary formations covered with acomplex of quaternary sediments. The oldest sediments, drilled at a depth of 270 m, aremarls and limestones of the Upper Cretaceous. Above, there are sandy-dusty Oligocenedeposits with glauconite, with a thickness of 60–90 m, then Miocene silts (with brown coal)up to several meters thickness, and the Pliocene layer formed as variegated clays (Tertiaryroof). The surface of the Pliocene and its thickness are strongly diversified as a result ofglacitectonic processes. In the area of the landfill, the depth to the Pliocene roof ranges froma few to several meters, and locally, it is exposed on the surface in the north-western part.

It was revealed in our previous study [22,23] that the landfill subsoil consists of sandysoils (thickness in range 2–15 m). In the south-eastern part of the area, the thickness of sandysediments is significant (locally up to 20 m) due to the presence of erosion-denudationdepressions in the top of the glacial tills and the existence of a small valley form (a smallwatercourse in the past). Towards the north, the thickness of the surface sandy sedimentsis small, and, in places, it fades into till clays with numerous sand pockets. Sandy layerswith organic and mud interbedding at the northern border of the landfill are associatedwith aeolian-lake formations in the vicinity of the Lipkowska Woda stream.

The first groundwater level was measured at the depth 0.3–2 m below the surface level,with fluctuations dependent on the weather and the local drainage conditions. The deeperpart of the subsoil consists of low permeable boulder and varved clays, with thickness25–40 m, and average hydraulic conductivity at 10−9 m/s. Low hydraulic gradients inthe south and east part of the area adjacent to the landfill result in very low velocity ofthe groundwater flow (inflow to the landfill). It was measured that the groundwater levelincreases from approximately 0.25 m in the south part to more than 0.75 m in the north-west

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part of the landfill site. Small increase of 0.2 m of the groundwater level was observed inthe south part of the landfill. Along the downstream direction from the landfill, the velocityof groundwater flow in sandy soils is about 5.8 × 10−7 m/s (for a hydraulic gradient 10‰).

Initially, the protection system against the contamination was not applied at the landfillsite. Since 1994, the reclamation works have been implemented. At that time, the solutionsof stability improvement were introduced. Moreover, the mineral capping, planting ofslopes, and installation of drainage and recirculation system were applied. One of the mostimportant solutions introduced at the landfill, as an effect of reclamation works, was theinstallation of bentonite vertical barrier [24]. The function of the vertical barrier applicationwas to minimize the migration of contaminants to the soil–water environment. The verticalbarrier (width 0.6 m) was installed at a depth of 2 m below the top of the clayey soils, atthe level 3.5–22 m below the surface. The permeability of the vertical barrier was below10−9 m/s (subsoil practically impermeable) [23].

The monitoring network of groundwater quality at the landfill and its surroundingsconsists of eleven piezometers (Figure 1). Nine of them (P-2A, P-7A, P-9, P-10A, P-11A,P-12A, P-14A, P-15, P-17) are located downstream to the landfill and reflect the possibleimpact of the landfill on the quality of groundwater. Two piezometers (P-4 and P-6A) arelocated upstream to the landfill and reflect the background quality of groundwater.

2.1.2. Zdounky Landfill

The Zdounky landfill (49◦14′29.2′′ N 17◦18′30.3′′ E) is located in the area of Netcice,part of the municipality of Zdounky in the Kromeríž district in the Zlín Region in theCzech Republic. The Zdounky landfill is classified to the S-OO3 group. The landfill wasconstructed at agricultural land of an area of approximately 10 ha. Currently, the landfillcovers an area of approximately 7 ha. The object was designed to carry a volume of907,000 m3 of wastes, with the idea of serving for a population of 75,000 people. The totalamount of deposited waste in the landfill is 1,280,750 Mg [25].

The surroundings of the Zdounky landfill are built of Paleogene rocks of marineorigin, belonging to the Outer flysch and the Magura flysch. In terms of regional geologicalstructure, the site is situated on the edge of the Carpathian mountain-forming system. TheOlšinka depression between Chriby and Litencické foothhill is filled with rocks of the outerCarpathian flysch. The local translucent sediments are included in the Ždánice—Hustopeceformation in the facies of calcareous clays, saliva, and sandstones of the mantle. Towardsthe Litencické hills, the frontal depth is already formed, and is filled by the predominantsaliva calcareous clays and clays with a thickness of about 500–700 m. Claystones, atvarious degrees of weathering, were identified at the landfill area by drilling. There are nosignificant differences between the sub-flysch units, and therefore, the area is characterizedwith a common fractured permeability. The hydrographic axis of the area is the Lipinkastream, which flows on the western edge of Zdounky into the stream Olšinka with anaverage flow at the mouth of 0.13 m3 s−1.

The depth to groundwater table is ranging from 4 to 14 m below the surface level. Thehydraulic gradient is almost equal to 70‰. The groundwater level fluctuates significantly.Relatively significant changes are registered over time and year-on-year. A significantfluctuation of groundwater levels is characteristic of a low-permeable environment (with alow active porosity). The piezometric level occurs in the formation of quaternary clayeysoils, forming the artesian “ceiling” of the deeper aquifer. The aquifer thickness is rangingfrom few to several meters.

For the Zdounky landfill, the base sealing system consists of several layers, includ-ing the mineral liner of clayey soil of a thickness 1 m, the geomembrane of high densitypolyethylene (HDPE) of 1.5 mm thickness and a drainage layer composed of sandy mate-rials and used tires. Water that comes into contact with wastes and is therefore (or couldpotentially be) contaminated is treated separately from rainwater and never comes intocontact with the soil environment.

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The monitoring network of groundwater quality at the landfill and its vicinity consistsof six piezometers (Figure 2).

Figure 2. The view on the Zdounky landfill location together with its monitoring network and surroundings.

One piezometer (MV-1) is located downstream the landfill and therefore is treatedas a monitoring point that reflects the impact of the landfill on groundwater quality. Therest of piezometers (MV-2A, MV-2B, MV-4, MV-5, and MV-6) are located upstream tothe landfill and reflect the background and the possible impact of surrounding areas ongroundwater. The piezometer MV-2B is a replaced monitoring of MV-2A. The monitoringpoints MV-4 and MV-5 reflect the groundwater quality at the east site of the landfill andmay be influenced by the runoff of contaminants from the surrounding arable lands. TheMV-5 monitoring point can be also directly affected by the runoff of contaminants from thesector intended to the storage of the construction and demolition wastes. The piezometerMV-6, due to its location, does not indicate the possible adverse effect of the landfill on thegroundwater, nevertheless can reflect the impact of arable lands on groundwater quality.

2.2. Sampling and Experimental Analysis

Groundwater samples were collected twice a year, in spring (I) and in autumn (II), inaccordance with the procedure outlined in PN-EN ISO 5667-3:2013-05 [26] and PN-ISO5667-11:2004 [27] standards.

The measurements of HMs were started straight away after the collection of thesamples. To assure the appropriateness of sampling, each sample was accompanied withthe measurement of pH, temperature, and EC. All samples were collected into smokedglass bottles and stored at a temperature of 1–5 ◦C. The assessment of groundwater qualityat the landfill site was based on a comparison of metal concentration measured in collectedsamples with standards provided by environmental laws (Table 1).

Moreover, for the Czech landfill, the monitoring results were compared with theso-called “critical values”, obtained from a long-term monitoring of groundwater qualityat the landfill and its surroundings. The selected “critical” values were in accordance withthe operating rules of landfills in the Czech Republic.

The analysed areas are low urbanized and the water from shallow water intakes isused for economic and municipal purposes. Due to that, the monitoring results of waterquality were also compared with the limit values set for drinking water, established by theWorld Health Organization (WHO).

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In the performed study, the monitoring period 2008–2018 was taken into considerationfor the purpose of groundwater quality assessment at landfill sites.

Table 1. Standards of water quality according to the national and international law.

Standard SpecificValue

Crtotal[mg L−1]

Zn[mg L−1]

Pb[mg L−1]

Cd[mg L−1]

Hg[mg L−1]

Ireland’s EPA, 2001 [28] I/PV 0.05 - 0.01 0.005 0.001

US EPA, 2018 [29]MCLG 0.1 - 0 0.005 0.002MCL 0.1 - - 0.005 0.002

SDWR - 5 - - -WHO [30] - 0.05 1 0.01 0.003 0.006

Polish Regulation a [31] - 0.05 0.01 0.005 0.001Polish Regulation b [32] - 0.05 1 0.1 0.005 0.001

Geochemical bacground [32] - 0.0001–0.010 0.005–0.050 0.001–0.010 0.0001–0.0005 0.00005–0.001

Notes: PV—the parametric value, which refers to the residual monomer concentration in the water as calculated according to specificationsof the maximum release from the corresponding polymer in contact with the water, MCLG—Maximum Contaminant Level Goal, set at alevel at which no known or anticipated adverse effect on the health of persons is expected to occur and which allows an adequate margin ofsafety, MCL—Maximum Contaminant Level set as the highest level of a contaminant that is allowed in drinking water, SDWR—SecondaryDrinking Water Regulations, a—limits set for drinking water, b—the limit values for “III” groundwater quality class (threshold values forgood chemical status).

2.3. Assessment of the HM Pollution Level

In order to provide an overview of water quality with respect to the content of HMs,the Heavy Metal Evaluation Index (HEI) was calculated. The HEI index was determinedusing the following formula [33]:

HEI =n

∑i=1

Hc

Hmax(1)

where:Hc—monitored value of i-th heavy metal; Hmax—maximum admissible concentration

of i-th HM, according to WHO [30].On the basis of HEI index the quality of water was assessed, concerning the follow-

ing interpretations of the results: HEI < 10 indicates low level of contamination, 10 <HEI < 20 indicates medium level of contamination, and HEI > 20 indicates high level ofcontamination [34].

The second measure applied for the evaluation of water quality, in terms of HMs, wasHeavy Metal Pollution Index (HPI). This parameter allows for the determination of anoverall quality of drinking water, using the following equations [35].

HPI = ∑ni=1 Wi·Qi

∑ni=1 Wi

(2)

Qi =n

∑i=1

|Mi − Ii|Si − Ii

× 100 (3)

where:Wi—unit weight of the i-th HM, Qi—sub-index of the i-th HM, n—number of consid-

ered HM, Mi—monitored value of the-th HM, Ii- ideal value of the i-th HM, Si—standardvalue of the i-th HM.

Regarding the HPI index, the quality of water was classified assuming that: HPI < 100indicates low contamination by HMs, HPI = 100 indicates the threshold value, and HPI > 100indicates high contamination by HMs. It is also required that the water characterized bythe HPI > 100 cannot be used for drinking purposes.

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3. Results3.1. Temporal Distribution of HMs in Groundwater

In the case of Radiowo landfill, it was revealed that the concentrations of totalchromium (Crtotal) in groundwater were many times lower than acceptable for goodgroundwater chemical status (Figure 3).

Figure 3. Temporal distribution of Crtotal in groundwater at the Radiowo landfill site.

The maximum concentrations of the Crtotal did not exceed 0.01 mg/L. The maximumvalues of this parameter were measured in piezometer P-9A (located downstream thelandfill). Increased concentrations of Crtotal, however not exceeding the limit values, canbe also the result of the location of this piezometer in the vicinity of the metallurgical pro-duction area (possible runoff of contaminants). The maximum concentrations of the Crtotalexceeding the range of values typical for the chemical background (0.0001–0.010 mg/L)can also indicate the possible impact of additional external sources of contamination.

The results of the monitoring studies performed at the Zdounky landfill indicateincidental peaks of Crtotal concentration in several piezometers (Figure 4). This situationcan be clearly visible in piezometer MV-5, where the concentrations were even three timeshigher than the WHO standard [30] and the level required for the good chemical status ofgroundwater [30]. Incidentally, the concentrations were also elevated in piezometers MV-1,MV-4, MV-2A/B, and MV-6. These concentrations were not directly related to the possibleimpact of the landfill, as these piezometers are located at the upstream direction from thelandfill, and therefore reflect only the possible influence of surroundings on groundwaterquality. The increased Crtotal concentrations in that case can be the effect of the runoff ofcontaminants from the storage sector of tires or construction and demolition wastes [36,37].

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Figure 4. Temporal distribution of Crtotal in groundwater at the Zdounky landfill site.

For both monitored landfills, it was observed that concentrations of Zn are below themaximum limit set for good chemical status of groundwater quality. For the Radiowolandfill, some temporal changes in Zn concentration and its fluctuations were observed(Figure 5).

Figure 5. Temporal distribution of Zn in groundwater at the Radiowo landfill site.

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The variability of Zn concentrations measured in piezometers can be attributed to thedevelopment of adjacent area and its possible impact on groundwater. Incidental increasein concentration of Zn may be due to the runoff from the adjacent street and the outflow ofcontaminants from the service area and production facilities.

At the Zdounky landfill site, for piezometers located downstream and upstreamfrom the landfill, slight Zn concentrations in groundwater were observed, characteristicfor the limits typical for the range of geochemical background (Figure 6). Therefore, thelandfill and its surroundings do not contribute to groundwater contamination by Zn at thestudy site.

Figure 6. Temporal distribution of Zn in groundwater at the Zdounky landfill site.

The concentrations of Pb measured in groundwater in the area of the Radiowo landfillwere below the limit set for the good chemical status (Figure 7).

In majority, the concentrations were in the range typical for the geochemical back-ground. There were only two peaks for the entire monitoring period where the concen-trations of Pb exceeded the value of 0.01 mg/L and therefore indicated that the waterdid not meet the requirements for water intended for human consumption. The similartendency was observed at the Zdounky landfill site, for which the concentrations of Pb ingroundwater indicated the good groundwater chemical status (Figure 8).

In 2008, the concentrations of Pb exceeded the limit set for the water intended fordrinking purposes. Almost throughout the entire monitoring period, the values of Pbwere in accordance with the limits of the concentrations characteristic for the geochemicalbackground.

For the Radiowo landfill, the Cd concentrations in groundwater indicate good chem-ical status (Figure 9). The values were characteristic for the geochemical backgroundand did not exceed the values subjected to the water intended for human consumption.This is very important from the point of view of the assessment of the landfill impact ongroundwater. Taking into consideration that Cd is very strongly adsorbed on muds, humus,and organic matter, leading to the possibility of entry to the food chain, and subsequentaccumulation in tissue, it is important to conduct thoughtful engineering activities thatwill not contribute to the release of this element to the environment [38].

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Figure 7. Temporal distribution of Pb in groundwater at the Radiowo landfill site.

Figure 8. Temporal distribution of Pb in groundwater at the Zdounky landfill site.

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Figure 9. Temporal distribution of Cd in groundwater at the Radiowo landfill site.

The concentrations of Cd at the Zdounky landfill (Figure 10) were slightly higher thanthose recommended by WHO for drinking water. When it comes to other environmentalrequirements for drinking water quality, it can be stated that values of Cd observed atthe Zdounky landfill were in accordance with the limits set by law [29]. In general, incomparison with the requirements for groundwater quality, the concentrations of Cd ingroundwater indicated its good chemical status.

Figure 10. Temporal distribution of Cd in groundwater at the Zdounky landfill site.

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For both monitored landfills, the concentrations of Hg were measured in rangescharacteristic for the geochemical background (Figures 11 and 12).

Figure 11. Temporal distribution of Hg in groundwater at the Radiowo landfill site.

Figure 12. Temporal distribution of Hg in groundwater at the Zdounky landfill site.

There was no impact of the landfills on groundwater observed, in terms of Hg pollu-tion. The requirements indicating good groundwater chemical status were met, as well as

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the limit set for drinking water was not exceeded. The results showed that the landfillsand their surrounding facilities had no adverse influence on the Hg concentrations ingroundwater.

Based on the results of statistical evaluation (Appendix A, Tables A1–A5), it was alsochecked what the form of HMs distribution is by using the measure of skewness [39] andkurtosis [40]. It was revealed that Crtotal concentrations in groundwater at Radiowo landfillsite are highly skewed for each piezometer within the monitoring network. In contrast,for the Zdounky landfill, it was obtained that the distribution of Crtotal is approximatelysymmetric (Table A1). The calculated values of kurtosis indicated that the distributionof Crtotal in groundwater is leptokurtic for each piezometer at the Radiowo landfill site,whereas for the Zdounky landfill, in each of the piezometers, the distribution of thiselement was defined as platykurtic.

Regarding Zn concentrations in groundwater, it was found that the distribution ishighly skewed for the Radiowo landfill. The same phenomenon was observed for almosteach piezometer at the Zdounky landfill, with the exception of the piezometer MV-6(distribution of Zn moderately skewed). For both landfill sites it was indicated that withregards to the values of kurtosis, the distribution of Zn are leptokurtic (Table A2).

As presented in Tables A3–A5, it was also revealed that the distribution of Pb, Cd,and Hg in groundwater at the Radiowo landfill is almost always highly skewed for eachpiezometer. The same tendency was also observed for the Zdounky landfill. The distribu-tion of Pb in groundwater at the Radiowo landfill is characterized as leptokurtic, excludingpiezometers P-9 and P-11A, for which the distribution can be defined as platykurtic. Someexceptions are also visible for the Zdounky landfill in which the distribution of Pb isleptokurtic for each piezometers, excluding MV-5.

3.2. Assessment of Groundwater Contamination by HMs Using Indices

By the HEI indices calculated for both analysed landfills, it was stated that the watercan be classified as low contaminated by HMs (Figure 13).

Figure 13. Comparison of HEI index between Radiowo and Zdounky landfill.

For the Radiowo landfill, the HEI index calculated based on piezometers locateddownstream the landfill was lower than for piezometers located at the upstream directionfrom the landfill. It may indicate that more significant impact on groundwater qualitymay have surrounding facilities than the landfill itself. For the Zdounky landfill, theHEI index calculated on the basis of data from piezometers located at the upstream and

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downstream the landfill were equal to 1.20 and 1.19, respectively. It may suggest that theZdounky landfill had almost the same impact on groundwater contamination by HMsas surrounding areas. Because the possible impact of the landfill on groundwater canbe evaluated by the analysis of observations from piezometers located downstream thelandfill, it can be stated that the Zdounky landfill had greater potential to pollute thegroundwater, in terms of HMs, than the Radiowo landfill. Regarding the HPI indices, it canbe indicated that both landfills did not affect the groundwater in aspect of the deteriorationof water quality for human consumption (Figure 14).

Figure 14. Comparison of HPI index between Radiowo and Zdounky landfill.

The threshold value of HPI = 100 was not exceeded. The values of HPI obtained atthe lower level for piezometers located downstream the landfill than upstream the landfillpointed out that the surrounding areas may have greater impact on groundwater qualitythan the existence and operation of the landfill.

4. Discussion

Several studies have confirmed that the occurrence of HMs in groundwater can betreated as an indicator of the leakage of leachates from the landfill body [41,42]. Theoutcomes of presented study may suggest that properly applied sealing and technical pro-tection of MSW landfills have significant effect on the reduction in groundwater pollutionby HMs. This was evidenced by both the results from the 10-year monitoring period andthe calculated HM pollution indices, which are one the most important methods of waterquality evaluation. These measures facilitate the classification of water in terms of theirutilization for drinking purposes [43]. However, a significant attention should be paid toincidental increases in concentrations of HMs in groundwater. Although HM pollutionindices allow for a global assessment of water quality, including its suitability for humanconsumption, they do not highlight the alarming increases in the concentration of HMs(for example, Crtotal at the Zdounky landfill site for current study).

The groundwater contamination by HMs is a global problem, often related to theimpact of landfills on the deterioration of water resources. In the case of the analysedlandfills, no significant impact on groundwater quality was demonstrated, especially dueto the application of an effective protection system against the contamination. The role ofengineering solutions was highlighted also by Zeng et al. [44] who stated that Tibet wastelandfills with effective liners caused no significant impact on groundwater contamination atMSW landfill sites. Nevertheless, even if the landfill is properly designed, some emergency

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cases can occur. The most probable reason of contamination near engineered landfill mayresult from the failure of the leachate collecting system (well, pipeline, pumping system)and the rapture of geomembrane [45]. The degradation of geomembrane associated withmaterial aging and defect evolution, may increase leachate leakage significantly. Despitethe fact that the impact of leachate leakage on surrounding groundwater may be smallin the short term, it begins to increase in the medium term, whereas in the long term, theprobability of groundwater pollution may reach 100% [46].

For the analysed sites, the greater impact on groundwater quality had neighbouringareas than the landfills. Low concentrations of HMs in groundwater, as revealed in studyperformed at the Radiowo landfill, may be also due to high adsorption of HMs in theunsaturated zone [47,48].

Nevertheless, in many regions of the world, landfills directly cause an increase in theconcentration of HMs in groundwater. The study performed by Murtaza et al. [15] revealedthat concentrations of Cd, Cu, Pb, and As in groundwater were higher than the permissiblelimit (60% of monitored samples exceeded the WHO limit). The increased levels of HMs ingroundwater were attributed to the leaching of contaminants from the landfill body [49].The leachate percolation and migration is also frequently evident from the quality ofgroundwater near uncontrolled landfills. For example, it was observed for the landfill inIndia (Kolkata) that groundwater quality may be affected by the leachate percolation andmigration. In that case, it was found for not engineered landfill that major ions, includingHMs, in groundwater were found to be high, indicating the influence of landfill leachateintrusion to groundwater [50]. The other sources of HMs contribution in the landfillarea may be open wastewater drains, industrial, and intensive agricultural activities [47].Generally, the problem of groundwater pollution exists in developing countries wherethe landfills are not properly engineered to prevent the release of contaminants [51]. Forexample, in the research performed by Amano et al. [52] in Ghana, it was found thatthe quality of water resources at the landfill site were above the limit for drinking waterbased on HPI index. They also revealed that the concentrations of Cd in surface waterand groundwater, within the surrounding area of the waste landfill site, were extremelyhigh. The literature findings also indicate the elevated concentrations of Pb in groundwaternear landfills, as well as the pollution caused by Cu and Cr which may contribute to thetoxicological risk at landfill sites [53–55]. The problem of environmental contaminationis also visible, with respect to the occurrence of Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo,Ni, Pb, V, and Zn in groundwater, which may also affect the human health [56]. Theoccurrence of toxic HMs may be due to plastics, batteries, leather, metallic items, paintproducts, fluorescent lamps, metal scrap, and steel industrial waste from the surroundingareas [49]. In context of our findings, increased concentrations of HMs in groundwaterwere observed for Cr at Zdounky landfill, what was attributed to the direct impact of therunoff of contaminants from the area of tires and demolition waste storage.

The results of several studies described above indicate that the groundwater contami-nation at the landfill sites should be a concern. Groundwater quality assessment should becarried out with systematic measurements of HMs concentrations in groundwater for thepurposes of determining the causes of alarming changes and taking corrective measures.It is also required to prevent other secondary pollutions, including air pollution and soilpollution [57].

5. Conclusions

Properly managed MSW landfills do not have to be regarded as the threat to theenvironment. The nuisances related to their existence can be reduced to minimum whilethe sealing system is used, or the reclamation works are successively applied at the landfillsite. Applied engineering activities may contribute to SD in the region of the landfill andalso may improve the quality of human life. Thanks to applied protection systems, thepeople are not exposed to the direct impact of toxic substances arising from the landfills.The establishing of a monitoring network of groundwater quality is also helpful when

Sustainability 2021, 13, 7769 16 of 20

assessing the impact of the landfill on groundwater as well as when checking the impact ofsurrounding areas on the groundwater deterioration.

Author Contributions: Conceptualization, A.P., A.J., M.D.V. and E.K.; methodology, A.P., A.J., M.D.V.and E.K.; software, A.P.; validation, A.P., A.J., M.D.V. and E.K.; formal analysis, A.P.; investigation,A.P., A.J., M.D.V. and E.K.; resources, M.D.V. and E.K.; data curation, A.P.; writing—original draftpreparation, A.P. and A.J.; writing—review and editing, A.P., M.D.V. and E.K..; visualization, A.P.and A.J.; supervision, M.D.V. and E.K.; project administration, A.P.; funding acquisition, A.P. andE.K. All authors have read and agreed to the published version of the manuscript.

Funding: This research was supported by the National Science Centre, Poland, under a grant No.2017/25/N/ST10/00909.

Institutional Review Board Statement: Not applicable.

Informed Consent Statement: Not applicable.

Data Availability Statement: Data sharing is not applicable to this article.

Conflicts of Interest: The authors declare no conflict of interest.

Appendix A

Table A1. Summary of statistical evaluation of Crtotal [mg/L] content in groundwater at the Radiowo and Zdounkylandfill sites.

Piezometer Mean Median Minimum Maximum Variance Standard Deviation Skewness Kurtosis

Radiowo landfillP2-A 0.010 0.010 0.010 0.012 0.000 0.001 2.232 3.898P-4 0.010 0.010 0.010 0.010 0.000 0.000 n.d. n.d.

P-6A 0.010 0.010 0.010 0.010 0.000 0.000 n.d. n.d.P-7A 0.010 0.010 0.010 0.011 0.000 0.000 4.690 22.000P-9 0.012 0.010 0.010 0.030 0.000 0.005 3.352 12.267

P-10A 0.011 0.010 0.010 0.018 0.000 0.002 3.877 15.730P-11A 0.011 0.010 0.010 0.018 0.000 0.002 3.954 16.185P-12A 0.010 0.010 0.010 0.010 0.000 0.000 n.d. n.d.P-14A 0.010 0.010 0.010 0.010 0.000 0.000 n.d. n.d.P-15 0.010 0.010 0.000 0.018 0.000 0.003 −1.043 11.007P-17 0.010 0.010 0.010 0.010 0.000 0.000 n.d. n.d.

Zdounky landfillMV-1 0.04 0.04 0.00 0.12 0.00 0.03 0.25 −0.15

MV-2 A/B 0.04 0.04 0.00 0.10 0.00 0.03 0.12 −0.96MV-4 0.04 0.04 0.00 0.09 0.00 0.03 −0.12 −1.11MV-5 0.05 0.05 0.00 0.15 0.00 0.04 0.49 −0.33MV-6 0.04 0.04 0.00 0.12 0.00 0.03 0.34 −0.31P2-A 0.046 0.050 0.005 0.071 0.000 0.013 −1.898 5.738

n.d.—not defined.

Table A2. Summary of statistical evaluation of Zn [mg/L] content in groundwater at the Radiowo and Zdounky landfill sites.

Piezometer Mean Median Minimum Maximum Variance Standard Deviation Skewness Kurtosis

Radiowo landfillP-4 0.042 0.050 0.005 0.057 0.000 0.016 −1.601 1.380

P-6A 0.043 0.050 0.007 0.050 0.000 0.013 −1.788 2.108P-7A 0.045 0.050 0.004 0.060 0.000 0.016 −2.100 3.482P-9 0.059 0.050 0.032 0.171 0.001 0.030 3.143 10.982

P-10A 0.072 0.050 0.009 0.380 0.006 0.079 3.223 11.738P-11A 0.059 0.050 0.015 0.289 0.003 0.053 4.253 19.287P-12A 0.052 0.050 0.012 0.152 0.001 0.024 3.553 16.294

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Table A2. Cont.

Piezometer Mean Median Minimum Maximum Variance Standard Deviation Skewness Kurtosis

P-14A 0.105 0.080 0.050 0.360 0.006 0.079 2.397 5.745P-15 0.065 0.050 0.020 0.252 0.003 0.056 2.881 7.807P-17 0.107 0.050 0.008 0.930 0.043 0.207 3.594 13.116

Zdounky landfillMV-1 0.016 0.020 0.000 0.027 0.000 0.009 −1.271 −0.111

MV-2 A/B 0.025 0.020 0.000 0.114 0.001 0.026 2.316 6.489MV-4 0.019 0.020 0.000 0.094 0.000 0.019 2.877 11.715MV-5 0.016 0.020 0.000 0.027 0.000 0.009 −1.232 −0.155MV-6 0.016 0.020 0.000 0.036 0.000 0.010 −0.741 0.255

Table A3. Summary of statistical evaluation of Pb [mg/L] content in groundwater at the Radiowo and Zdounky landfill sites.

Piezometer Mean Median Minimum Maximum Variance Standard Deviation Skewness Kurtosis

Radiowo landfillP2-A 0.005 0.004 0.001 0.010 0.000 0.002 1.775 3.717P-4 0.005 0.004 0.001 0.019 0.000 0.004 2.886 9.544

P-6A 0.005 0.004 0.001 0.010 0.000 0.002 1.787 3.853P-7A 0.004 0.004 0.001 0.010 0.000 0.002 1.419 3.403P-9 0.005 0.004 0.001 0.012 0.000 0.003 1.529 2.077

P-10A 0.005 0.004 0.001 0.010 0.000 0.002 1.787 3.853P-11A 0.005 0.004 0.001 0.010 0.000 0.002 1.505 2.650P-12A 0.005 0.004 0.001 0.010 0.000 0.002 1.779 3.846P-14A 0.005 0.004 0.001 0.010 0.000 0.002 1.787 3.853P-15 0.005 0.004 0.001 0.010 0.000 0.002 1.787 3.853P-17 0.005 0.004 0.001 0.010 0.000 0.002 1.787 3.853

Zdounky landfillMV-1 0.008 0.007 0.000 0.070 0.000 0.014 4.336 19.809

MV-2 A/B 0.009 0.007 0.000 0.070 0.000 0.014 4.238 19.156MV-4 0.008 0.007 0.000 0.070 0.000 0.014 4.303 19.596MV-5 0.054 0.045 0.000 0.150 0.002 0.043 0.489 −0.334MV-6 0.009 0.007 0.000 0.070 0.000 0.015 3.569 13.791

Table A4. Summary of statistical evaluation of Cd [mg/L] content in groundwater at the Radiowo and Zdounky landfill sites.

Piezometer Mean Median Minimum Maximum Variance Standard Deviation Skewness Kurtosis

Radiowo landfillP2-A 0.0004 0.0003 0.0003 0.0010 0.0000 0.0002 2.1061 3.4662P-4 0.0004 0.0003 0.0003 0.0010 0.0000 0.0002 2.1061 3.4662

P-6A 0.0004 0.0003 0.0003 0.0010 0.0000 0.0002 2.1061 3.4662P-7A 0.0004 0.0003 0.0003 0.0007 0.0000 0.0001 2.2065 3.7459P-9 0.0004 0.0003 0.0003 0.0010 0.0000 0.0002 2.1061 3.4662

P-10A 0.0004 0.0003 0.0003 0.0010 0.0000 0.0002 2.1061 3.4662P-11A 0.0004 0.0003 0.0003 0.0010 0.0000 0.0002 2.0789 3.4079P-12A 0.0004 0.0003 0.0003 0.0010 0.0000 0.0002 2.1061 3.4662P-14A 0.0004 0.0003 0.0003 0.0010 0.0000 0.0002 2.1061 3.4662P-15 0.0004 0.0003 0.0003 0.0010 0.0000 0.0002 2.1061 3.4662P-17 0.0005 0.0003 0.0003 0.0020 0.0000 0.0004 2.9317 9.5506

Zdounky landfillMV-1 0.0031 0.0040 0.0000 0.0040 0.0000 0.0017 −1.3988 −0.0572

MV-2 A/B 0.0031 0.0040 0.0000 0.0040 0.0000 0.0017 −1.3988 −0.0572MV-4 0.0031 0.0040 0.0000 0.0040 0.0000 0.0017 −1.3988 −0.0572MV-5 0.0031 0.0040 0.0000 0.0040 0.0000 0.0017 −1.3988 −0.0572MV-6 0.0031 0.0040 0.0000 0.0040 0.0000 0.0017 −1.3988 −0.0572

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Table A5. Summary of statistical evaluation of Hg [mg/L] content in groundwater at the Radiowo and Zdounky landfill sites.

Piezometer Mean Median Minimum Maximum Variance Standard Deviation Skewness Kurtosis

Radiowo landfillP2-A 0.0001 0.0001 0.0001 0.0005 0.0000 0.0002 2.2082 3.2965P-4 0.0001 0.0001 0.0001 0.0005 0.0000 0.0002 2.2082 3.2965

P-6A 0.0001 0.0001 0.0001 0.0005 0.0000 0.0002 2.2082 3.2965P-7A 0.0001 0.0001 0.0001 0.0005 0.0000 0.0002 2.2082 3.2965P-9 0.0001 0.0001 0.0001 0.0005 0.0000 0.0002 2.2082 3.2965

P-10A 0.0001 0.0001 0.0001 0.0005 0.0000 0.0002 2.2082 3.2965P-11A 0.0001 0.0001 0.0001 0.0005 0.0000 0.0002 2.2082 3.2965P-12A 0.0001 0.0001 0.0001 0.0005 0.0000 0.0002 2.2082 3.2965P-14A 0.0001 0.0001 0.0001 0.0005 0.0000 0.0002 2.2082 3.2965P-15 0.0001 0.0001 0.0001 0.0005 0.0000 0.0002 2.2082 3.2965P-17 0.0001 0.0001 0.0001 0.0005 0.0000 0.0002 2.2082 3.2965

Zdounky landfillMV-1 0.0008 0.0010 0.0000 0.0010 0.0000 0.0004 −1.3988 −0.0572

MV-2 A/B 0.0008 0.0010 0.0000 0.0010 0.0000 0.0004 −1.3988 −0.0572MV-4 0.0008 0.0010 0.0000 0.0010 0.0000 0.0004 −1.3988 −0.0572MV-5 0.0010 0.0010 0.0000 0.0050 0.0000 0.0010 3.2508 13.8396MV-6 0.0008 0.0010 0.0000 0.0010 0.0000 0.0004 −1.3988 −0.0572

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